For much of 2009, prices in the petroleum complex have been bumping along, trying to form a solid bottom.

Although I can't tell you exactly when and where the exact bottom will be, the same forces that drove prices sky-high are still lurking in the background, waiting for a chance to reassert themselves.

On the supply side, the cost of finding and producing fossil fuels continues to surge. The easy-to-get-at resources are gone. On the demand side, 3 billion people in the emerging markets are clamoring to drive cars, trucks, buses, tractors and other petroleum-powered machinery.

Until a bottom for energy prices comes more clearly into view, I suggest a cautious approach to the sector. Focus on investments that throw off a generous cash income here and now.

Play it Safe With Master Limited Partnerships (MLPs)

At the head of my energy shopping list these days are publicly traded master limited partnerships (MLPs) that operate pipelines and related infrastructure.

Typically, these toll-taker businesses aren't directly exposed, in any great degree, to fluctuating prices for oil or natural gas. MLPs collect a fee for transporting the stuff, and sometimes for processing or storing it; they don't drill for it or peddle it to the end user.

On the other hand, to cover their fixed costs, energy MLPs require a steady volume of goods passing through the pipes. Of late, the economic downturn has crimped sales of refined products (like gasoline and jet fuel). However, pipelines that handle mostly natural gas have continued to thrive. Those are the names I favor for new purchases.

When choosing an MLP, it's important to look beyond yield alone. Building and maintaining a pipeline costs lots of money, so you want to own partnerships that can tap the debt and equity markets even in today's unsettled climate. The MLPs on my recommended list are well financed for 2009 and beyond, with ample cash flow to cover quarterly distributions to the unitholders (you and me).

NEXT: Two Top MLPs to Buy Now